Large-Amplitude Mountain Waves in the Mesosphere Accompanying Weak Cross-Mountain Flow During DEEPWAVE Research Flight RF22
Journal Article - Open Access
NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States
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Mountain wave MW propagation and dynamics extending into the upper mesosphere accompanying weak forcing are examined using in situ and remote-sensing measurements aboard the National Science FoundationNational Center for Atmospheric Research Gulfstream V GV research aircraft and the German Aerospace Center Falcon. The measurements were obtained during Falcon flights FF9 and FF10 and GV Research Flight RF22 of the Deep Propagating Gravity Wave Experiment DEEPWAVE performed over Mount Cook, New Zealand, on 12 and 13 July 2014. In situ measurements revealed both trapped lee waves having zonal wavelengths of xsimilar to 12km and less, and larger-scale, vertically propagating MWs primarily at xsimilar to 20-60km and similar to 100-300km extending from west to similar to 400km east of Mount Cook. GV Rayleigh lidar measurements from 25- to 60-km altitudes showed that the weak forcing and zonal winds that increased from similar to 12ms at 12km to similar to 40 and 130ms at 30 and 55km, respectively, enabled largely linear MW propagation and strong amplitude growth with altitude into the mesosphere. GV Na lidar and airglow imager measurements revealed an extensive MW response from similar to 70 to 87km with large amplitudes and vertical displacements at xsimilar to 40-300km but with both decreasing with altitude approaching a critical level near 90km. These MWs exhibited large-scale MW breaking and among the largest sustained momentum fluxes observed in the mesosphere. UK Met Office Unified Model simulations of the RF22 MW event captured many aspects of the observed MW field and revealed that despite the dominant large-scale MW responses in the stratosphere, the major momentum fluxes accompanied smaller-scale waves.